This invention relates to signalling interfaces between Layer 2 (L2) and Layer 1 (L1) communication processes as defined by Open Systems Interconnection (OSI) specifications of the International Standards Organization (OSI). L2 processes provide data link control functions, whereas L1 processes relate directly to physical operations by which communication signals are sent and received. High speed telecommunication applications associated with multiplex transmission of voice and data, for instance signalling applications in primary rate ISDN (Integrated Systems Digital Network) environments of the type contemplated by CCITT specifications referenced herein, require efficient handling of signals between L2 and L1 processes to sustain required transmission signalling speeds. The present invention relates to an L1/L2 interface with improved signal transfer efficiency. The subject interface operates in a burst time division multiplex (BTDM) mode which is the basis for its improved efficiency.